TWI854267B - Fuel cell system and control method - Google Patents

Abstract

The embodiment provides a fuel cell system and a control method that can improve the responsiveness of the power generation output of the fuel cell system. The fuel cell system of the embodiment has: a plurality of fuel cells, and a control device that controls the operating state of each fuel cell. The control device has: an instruction acquisition unit that acquires an output instruction, a normal operation unit determination unit that determines the number of fuel cells to be operated in the normal operation mode, and an operation state determination unit that determines the operation state of each fuel cell. The operation state determination unit changes the operation mode of at least one of the fuel cells operating in the normal operation mode to the standby operation mode in accordance with the output instruction, or changes the operation mode of at least one of the fuel cells operating in the standby operation mode to the normal operation mode.

Description

Fuel cell system and control method

The implementation method of the present invention is related to a fuel cell system and a control method thereof. [Reference to related applications]

This application claims priority from Japanese Patent Application No. 2021-155993 (filing date: September 24, 2021). This application incorporates all the contents of the prior application by reference.

As a system that directly converts the chemical energy of fuel gas into electricity, the fuel cell system is widely known. The fuel cell system has a fuel cell that generates electricity by electrochemically reacting hydrogen, a fuel, with oxygen, an oxidant. Such a fuel cell system can obtain electricity with high power generation efficiency.

Here, improvement in the responsiveness of the power generation output of a fuel cell system to the required power generation output is sought.

The problem to be solved by the present invention is to provide a fuel cell system and a control method that can improve the responsiveness of the power generation output of the fuel cell system.

The fuel cell system of the embodiment comprises: a plurality of fuel cells and a control device for controlling the operation state of each fuel cell. Each fuel cell can operate in a plurality of operation modes, and the plurality of operation modes include: a normal operation mode for operating with a power output having a power generation efficiency higher than a first power generation efficiency, and a standby operation mode for operating with a power generation efficiency lower than the first power generation efficiency and lower than a second power generation efficiency. The control device comprises: an instruction acquisition unit, which acquires an output instruction indicating the total power output to be generated by the fuel cell system; a normal operation number determination unit, which determines the number of fuel cells to be operated in a normal operation mode based on the total power output indicated by the output instruction; and an operation state determination unit, which determines the operation state of each fuel cell based on the number of fuel cells determined by the normal operation number determination unit. In a case where the total power output indicated by the output instruction is lower than the total power output generated by the fuel cell system, or in a case where the number of fuel cells determined by the normal operation number determination unit is less than the number of fuel cells operating in the normal operation mode, the operation state determination unit changes the operation mode of at least one of the fuel cells operating in the normal operation mode to the standby operation mode; When the total power output indicated by the output instruction is higher than the total power output generated by the fuel cell system, or when the number of fuel cells determined by the normal operation number determination unit is greater than the number of fuel cells operating in the normal operation mode, the operation state determination unit changes the operation mode of at least one of the fuel cells operating in the standby operation mode to the normal operation mode.

Moreover, the control method of the implementation mode is a control method of a fuel cell system, which includes a plurality of fuel cells, each of which can operate in a plurality of operation modes, and the plurality of operation modes include: a normal operation mode in which the power generation output is operated with a high-efficiency power generation efficiency greater than a first power generation efficiency, and a standby operation mode in which the power generation efficiency is operated with a low-efficiency power generation output less than a second power generation efficiency lower than the aforementioned first power generation efficiency. The system comprises: an output instruction acquisition process for acquiring an output instruction indicating a total power output to be generated by the fuel cell system; a normal operation number determination process for determining the number of fuel cells to be operated in a normal operation mode based on the total power output indicated by the output instruction; and an operation state determination process for determining the operation state of each fuel cell based on the number of fuel cells determined in the normal operation number determination process. In the operation state determination step, when the total power output indicated by the output instruction is lower than the total power output generated by the fuel cell system, or when the number of fuel cells determined in the normal operation number determination step is smaller than the number of fuel cells operating in the normal operation mode, the operation mode of at least one of the fuel cells operating in the normal operation mode is changed to the standby mode. Operation mode; when the total power output indicated by the output instruction is higher than the total power output generated by the fuel cell system, or when the number of fuel cells determined in the normal operation number determination step is greater than the number of fuel cells operating in the normal operation mode, the operation mode of at least one of the fuel cells operating in the standby operation mode is changed to the normal operation mode. [Effect of the invention]

According to the present invention, the responsiveness of the power generation output of the fuel cell system can be improved.

＜First implementation method＞

The first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a block diagram showing the structure of a fuel cell system 1 according to the first embodiment of the present invention. Fig. 2 is a diagram for schematically explaining the structure of a fuel cell 10 included in the fuel cell system 1 shown in Fig. 1 .

The fuel cell system 1 shown in FIG. 1 includes a plurality of fuel cells 10, a control device 20, and an operating device 30.

The fuel cell 10 generates electricity using hydrogen and oxygen. Each fuel cell 10 is, for example, a polymer electrolyte fuel cell (PEFC). In the example shown in FIG. 2 , the fuel cell 10 includes a fuel cell stack 11, a fuel supply pipe 14, a fuel exhaust pipe 15, an air supply pipe 16, an air exhaust pipe 17, and a power supply device 18.

The fuel cell stack 11 includes an anode 12 and a cathode 13 which are arranged to surround an electrolyte membrane. A fuel supply pipe 14 is connected to the air intake port of the anode 12. The fuel supply pipe 14 supplies hydrogen to the anode 12. A fuel discharge pipe 15 is connected to the discharge port of the anode 12. The fuel discharge pipe 15 discharges the gas discharged from the anode 12 to the outside or inside of the fuel cell 10. An air supply pipe 16 is connected to the air intake port of the cathode 13. The air supply pipe 16 supplies oxygen in the air to the cathode 13. An air discharge pipe 17 is connected to the discharge port of the cathode 13. The air discharge pipe 17 discharges the gas discharged from the cathode 13 to the outside of the fuel cell 10.

The fuel cell stack 11 generates electricity using hydrogen supplied to the anode 12 through the fuel supply pipe 14 and oxygen in the air supplied to the cathode 13 through the air supply pipe 16 .

The power supply device 18 is connected to the electrodes of the fuel cell stack 11. The power supply device 18 obtains electric current from the fuel cell stack 11. In the example shown in the figure, the maximum power generation output of each fuel cell 10 is 100 kW.

The control device 20 controls the operation state of each fuel cell 10. Specifically, the control device 20 causes the fuel cell 10 to operate in a plurality of operation modes including a normal operation mode and a standby operation mode by sending a control signal to each fuel cell 10. Furthermore, the control device 20 causes the operation of the fuel cell 10 to be stopped, or causes the stopped fuel cell 10 to be started, by sending a control signal to each fuel cell 10. That is, each fuel cell 10 receives a control signal and becomes an operation state of any one of the state of operating in the normal operation mode, the state of operating in the standby operation mode, and the operation stop state.

Here, when the fuel cell 10 operates in the normal operation mode, it operates at a power output having a power generation efficiency greater than or equal to the first power generation efficiency. By making the power generation efficiency of the fuel cell 10 operating in the normal operation mode greater than or equal to the prescribed power generation efficiency, the power generation efficiency of the entire fuel cell system 1 can be made greater than or equal to the prescribed power generation efficiency. Furthermore, when the fuel cell 10 operates in the standby operation mode, it operates at a power output less than or equal to the second power generation efficiency that is lower than the above-mentioned first power generation efficiency. In the illustrated example, when the fuel cell 10 operates in the standby operation mode, the fuel cell system 1 is disconnected from the system that supplies power and operates independently.

In the illustrated example, when the fuel cell 10 is operated in the normal operation mode, it operates at a power output of 40% to 60% of the maximum power output of the fuel cell, or at a power output of 42% to 58%. In the illustrated example, when the fuel cell 10 is operated in the normal operation mode, it operates at a power output at which the power generation efficiency of the fuel cell 10 is the maximum. Generally, when the fuel cell 10 is operated at a power output of approximately 50% of the maximum power generation output of the fuel cell 10, its power generation efficiency is maximum. In the illustrated example, when each fuel cell 10 is operated in the normal operation mode, it operates at a power output of 50% of its maximum power generation output. As mentioned above, since the maximum power generation output of each fuel cell 10 in the illustrated example is 100kW, the power generation output of the fuel cell 10 operating in the normal operation mode is 50kW.

Furthermore, in the illustrated example, when the fuel cell 10 is operated in the standby operation mode, it is operated at a power generation output of 5 to 15% of the maximum power generation output of the fuel cell 10. In the illustrated example, when the fuel cell 10 is operated in the standby operation mode, it is operated at a power generation output of 10% of the maximum power generation output of the fuel cell 10. As described above, in the illustrated example, since the maximum power generation output of each fuel cell 10 is 100 kW, the power generation output of the fuel cell 10 operating in the standby operation mode is 10 kW.

Hereinafter, the fuel cell 10 operating in the normal operation mode is also referred to as the "normal mode fuel cell" or the "normal mode FC". Furthermore, hereinafter, the fuel cell 10 operating in the standby operation mode is also referred to as the "standby mode fuel cell" or the "standby mode FC". Furthermore, hereinafter, the fuel cell 10 in the operation stop state is also referred to as the "stop fuel cell" or the "stop FC". Furthermore, hereinafter, the power generation output of the fuel cell 10 operating in the normal operation mode is also referred to as the "normal power generation output". Furthermore, hereinafter, the power generation output of the fuel cell 10 operating in the standby operation mode is also referred to as the "standby power generation output".

Fig. 3 is a block diagram schematically showing the structure of the control device 20. As shown in Fig. 3, the control device 20 according to the first embodiment includes an information acquisition unit 21, a command acquisition unit 22, a normal operation number determination unit 23, and an operation state determination unit 24.

The information acquisition unit 21 acquires the number of normal mode fuel cells 10, the number of standby mode fuel cells 10, and the number of activations of each fuel cell 10. The number of normal mode fuel cells 10, the number of standby mode fuel cells 10, and the number of activations of each fuel cell 10 are input to the information acquisition unit 21, for example, from the operation state determination unit 24.

The command acquisition unit 22 acquires an output command indicating the total power output to be generated by the fuel cell system 1. In the illustrated example, the command acquisition unit 22 acquires the total power output from the operating device 30. Hereinafter, the total power output indicated by the output command is also referred to as the "command total power output". Furthermore, the total power output outputted by the fuel cell system 1 is also referred to as the "current total power output".

When the commanded total power output is different from the current total power output, the normal operation number determination unit 23 determines the number of fuel cells 10 to be operated in the normal operation mode based on the output command, and inputs the determined number to the operation state determination unit 24. The normal operation number determination unit 23 determines the number of fuel cells 10 to be operated in the normal operation mode based on the result of dividing the commanded total power output by the normal power output. For example, when the commanded total power output is 200kW and the normal power output is 50kW, the result of dividing the commanded total power output by the normal power output is 200kW/50kW=4. Therefore, the normal operation number determination unit 23 determines the number of fuel cells 10 to be operated in the normal operation mode to be four. Furthermore, when the commanded total power output is equal to the current total power output, no input is made from the normal operation unit number determination unit 23 to the operation state determination unit 24. Hereinafter, the number of fuel cells 10 to be operated in the normal operation mode determined by the normal operation unit number determination unit 23 is also referred to as the "command normal mode number".

The operation state determination unit 24 determines the operation state of each fuel cell 10 based on the commanded number of normal mode units determined by the normal operation unit number determination unit 23. When the commanded total power generation output is lower than the current total power generation output (therefore, when the commanded number of normal mode units is less than the number of normal mode fuel cells), the operation state determination unit 24 changes the operation mode of at least one normal mode fuel cell 10 to the standby operation mode. Moreover, when the commanded total power output is higher than the current total power output (therefore, the commanded number of normal mode units is greater than the number of normal mode fuel cells), the operating state determination unit 24 changes the operating mode of at least one standby mode fuel cell 10 to the normal operating mode, or changes the operating mode of at least one stopped fuel cell 10 to the normal operating mode.

For example, the normal power generation output is 50 kW, the number of normal mode fuel cells is five, and the current total power generation output is 250 kW. In this state, if an output command for a total power generation output of 200 kW is input, the normal operation number determination unit 23 determines the number of commanded normal mode fuel cells to be four. In this case, the operation state determination unit 24 changes the operation mode of one of the five normal mode fuel cells 10 to the standby operation mode.

Alternatively, for example, the normal power generation output is 50 kW, the number of normal mode fuel cells is three, and the current total power generation output is 150 kW. In this state, if an output command for a total power generation output of 200 kW is input, the normal operation unit number determination unit 23 determines the number of commanded normal mode units to be four. In this case, the operation state determination unit 24 changes the operation mode of one fuel cell other than the normal mode fuel cell 10 among the plurality of fuel cells 10 to the normal operation mode.

When changing the operation mode of the normal mode fuel cell 10 to the standby operation mode, the operation state determination unit 24 selects the fuel cell 10 to be changed to the standby operation mode as follows when there are a plurality of normal mode fuel cells 10. That is, the operation state determination unit 24 selects the fuel cell 10 having the smallest number of activation times acquired by the information acquisition unit 21 among the normal mode fuel cells 10 as the fuel cell whose operation mode is changed to the standby operation mode.

Furthermore, when changing the stopped fuel cell 10 to the normal operation mode, the operation state determination unit 24 selects the fuel cell 10 to be changed to the normal operation mode as follows when there are a plurality of stopped fuel cells 10. That is, the operation state determination unit 24 selects the fuel cell 10 having the smallest number of activations obtained by the information acquisition unit 21 among the stopped fuel cells 10 as the fuel cell to be changed to the normal operation mode.

Furthermore, when the number of standby mode fuel cells 10 obtained by the information acquisition unit 21 is greater than the prescribed number N, the operation state determination unit 24 determines the fuel cell 10 with the smallest number of startups obtained by the information acquisition unit 21 as the fuel cell 10 to be stopped among the standby mode fuel cells 10.

Thus, in the fuel cell system 1 of the first embodiment, when the number of normal mode fuel cells 10 is greater than the number of fuel cells 10 required for the output command total power generation output, the operation state of the excess normal mode fuel cells 10 is not immediately changed to the operation stop state, but is changed to the standby operation mode. Alternatively, in the fuel cell system 1 of the first embodiment, when the number of normal operation mode fuel cells 10 is less than the number of fuel cells 10 required for the output command total power generation output, the number of fuel cells 10 operating in the normal operation mode is increased, but at this time, if there are standby mode fuel cells 10, it is given priority to change the standby mode fuel cells 10 to the normal operation mode rather than stopping the fuel cells 10. By controlling the plurality of fuel cells 10 in this way, the chance of starting up the fuel cells 10 that are in a stopped state can be reduced while increasing the total power generation output of the fuel cell system 1. As a result, the responsiveness of the power generation output of the fuel cell system 1 can be improved.

Furthermore, in the fuel cell system 1 of the first embodiment, as the fuel cell 10 to be changed from the normal operation mode to the standby operation mode, the fuel cell 10 with the least number of starts and stops among the normal mode fuel cells 10 is selected. Furthermore, as the fuel cell 10 to be changed from the standby operation mode to the operation stop state, the fuel cell 10 with the least number of starts and stops among the standby mode fuel cells 10 is selected. By changing the fuel cell 10 with the least number of starts and stops from the normal operation mode to the standby operation mode, and further changing from the standby operation mode to the operation stop state, it is possible to suppress the bias in the number of starts and stops generated among the plurality of fuel cells 10. In other words, it is possible to prevent a situation where the number of starts and stops of some of the plurality of fuel cells 10 increases significantly compared to the number of starts and stops of other fuel cells 10. This prevents a situation where some of the plurality of fuel cells 10 deteriorate earlier than other fuel cells 10. As a result, the fuel cell system 1 can be operated with high reliability.

Furthermore, in the fuel cell system 1 of the first embodiment, as the fuel cell 10 that changes from the operation stop state to the standby operation mode, the fuel cell 10 that has been started and stopped the least is selected. This can also suppress the bias in the number of starts and stops among the plurality of fuel cells 10, and can suppress the situation where some of the plurality of fuel cells 10 deteriorate earlier than the other fuel cells 10.

Furthermore, as described above, when the commanded total power output is equal to the current total power output, no input is made from the normal operation unit number determination unit 23 to the operation state determination unit 24. Therefore, in this case, the operation state determination unit 24 does not change the operation state of each fuel cell 10. In other words, in this case, the operation mode of the normal mode fuel cell 10 is maintained in the normal operation mode, the operation mode of the standby mode fuel cell 10 is maintained in the standby operation mode, and the stop fuel cell 10 is maintained in the operation stop state.

Next, referring to FIG. 4 and FIG. 5 , the control method of the fuel cell system 1 is described. Here, the number of the plurality of fuel cells 10 included in the fuel cell system 1 is determined to be six, the maximum power generation output of each of the plurality of fuel cells 10 is determined to be 100 kW, and the normal power generation output of each fuel cell 10 is determined to be 50 kW. Furthermore, the command total power generation output is determined to be any one of 0 kW, 50 kW, 100 kW, 150 kW, 200 kW, 250 kW, and 300 kW.

As shown in FIG. 4 , the command acquisition unit 22 acquires an output command indicating the total power output (command total power output) that the fuel cell system 1 should generate from the operating device 30 (step S11 ).

Next, the normally operated unit number determination unit 23 determines whether the commanded total power output is equal to the current total power output (step S12). If the commanded total power output is equal to the current total power output ("Yes" in step S12), the operating state of each fuel cell 10 is maintained.

On the other hand, in step S12, when the commanded total power output is different from the current total power output ("No" in step S12), the normal operation number determination unit 23 determines whether the commanded total power output is greater than the current total power output (step S13). In step S13, the normal operation number determination unit 23 may also determine whether the value of the commanded total power output divided by the normal power output (the commanded normal mode number of units) is greater than the number of normal mode fuel cells 10. Next, when the commanded total power output is greater than the current total power output (or when the commanded number of normal mode units is greater than the number of normal mode fuel cells 10) ("Yes" in step S13), the normal operation unit number determination unit 23 transfers the commanded number of normal mode units to the operation state determination unit 24. Next, the operation state determination unit 24 obtains information on the number of standby mode fuel cells 10 from the information acquisition unit 21, and determines whether the number of standby mode fuel cells 10 is one or more (step S14). When the number of standby mode fuel cells 10 is one or more ("Yes" in step S14), the operation state determination unit 24 changes the operation mode of one standby mode fuel cell 10 to the normal operation mode (step S15). As a result, the fuel cell 10 operates in the normal operation mode. After that, the determination of step S12 is performed again. In step S15, the operation state determination unit 24 transfers the information related to the operation state of each fuel cell 10 to the information acquisition unit 21.

In step S14, if there is no standby mode fuel cell 10 ("No" in step S14), the operation state determination unit 24 changes the fuel cell 10 that has been started and stopped the least times among the stopped fuel cells 10 to the normal operation mode (step S16). As a result, the fuel cell 10 is started and operated in the normal operation mode. After that, the determination in step S12 is performed again.

Next, in step S13, a case where the commanded total power output is smaller than the current total power output (or the commanded number of normal mode units is smaller than the number of normal mode fuel cells 10) is described ("No" in step S13). In this case, the normal operation unit number determination unit 23 transfers the commanded number of normal mode units to the operation state determination unit 24. Next, in the operation state determination unit 24, information about the number of starts and stops of each fuel cell 10 is obtained from the information acquisition unit 21, and the operation mode of the fuel cell with the least number of starts and stops among the normal mode fuel cells 10 is changed to the standby operation mode (step S17). As a result, the fuel cell 10 operates in the standby operation mode. Thereafter, the operation state determination unit 24 determines whether the number of the standby mode fuel cells 10 is greater than the prescribed number N (step S18). In step S18, when it is determined that the number of the standby mode fuel cells 10 is greater than the prescribed number N ("Yes" in step S18), the operation state determination unit 24 sets the fuel cell 10 with the least number of starts and stops among the standby mode fuel cells 10 to the operation stop state (step S19). At this time, the number of fuel cells 10 that have been changed to the operation stop state is equal to the value obtained by subtracting the prescribed number N from the number of the standby mode fuel cells 10. This value represents the excess number of standby mode fuel cells 10. As a result of step S19, the standby mode fuel cells 10 with the least number of starts and stops are in the operation stop state only for the excess number. In step S19, the operation state determination unit 24 transfers the information on the operation state of each fuel cell 10 to the information acquisition unit 21. After that, the judgment of step S12 is performed again.

On the other hand, in step S18, when it is determined that the number of standby mode fuel cells 10 is less than the predetermined number N ("No" in step S18), the operation state determination unit 24 does not change the operation state of the standby mode fuel cells 10. In addition, the operation state determination unit 24 transfers the information on the operation state of each fuel cell 10 to the information acquisition unit 21. Then, the determination in step S12 is performed again.

Moreover, in the above-mentioned embodiment, in step S14, when there is no standby mode fuel cell 10 ("No" in step S14), the stopped fuel cell 10 is started, but it is not limited to this. In the case of "No" in step S14, when there is a fuel cell 10 in the multiple fuel cells 10 that has shifted from the standby operation mode (or the normal operation mode) to the operation stop state, the operation state determination unit 24 can also change the operation state of one fuel cell that has shifted to the operation stop state to the normal operation mode. In this way, the increase in the number of starts and stops of the fuel cell can be suppressed. <Second embodiment>

Next, referring to Figs. 6 to 8 , the fuel cell system 1 according to the second embodiment will be described. The fuel cell system 1 according to the second embodiment shown in Fig. 6 is different from the fuel cell system 1 according to the first embodiment in that the control device 20 includes a prediction command acquisition unit 25 and a standby operation unit number determination unit 26. The rest of the structure is substantially the same as that of the fuel cell system 1 according to the first embodiment shown in Figs. 1 to 5 . In the second embodiment shown in Figs. 6 to 8 , the same component symbols are given to the same parts as those in the first embodiment shown in Figs. 1 to 5 , and detailed descriptions are omitted.

The predicted instruction acquisition unit 25 acquires a predicted output instruction indicating the total power output that the fuel cell system 1 should generate in the future. In the illustrated example, the predicted output instruction is acquired by the predicted instruction acquisition unit 25 from the operating device 30. For example, the predicted output instruction indicating the total power output that the fuel cell system 1 should generate is input from the operating device 30 to the predicted instruction acquisition unit 25 every 20 minutes from 20 minutes to 40 minutes. In addition, hereinafter, the total power output indicated by the predicted output instruction is also referred to as the "predicted total power output".

The standby operation number determination unit 26 receives the input of the predicted output command and calculates the number of fuel cells 10 required to output the predicted total power output. Specifically, the number of fuel cells 10 required to output the predicted total power output is calculated by dividing the predicted total power output by the normal power output. Then, the calculated number is compared with the sum of the number of normal mode fuel cells 10 and the number of standby mode fuel cells 10 at the current time (at the time when the predicted output command is input). When the calculated number of units is greater than the above sum, the standby operation unit number determination unit 26 inputs the difference between the calculated number of units and the above sum as the number of fuel cells 10 to be changed from the operation stop state to the standby operation mode to the operation state determination unit 24. On the other hand, when the calculated number of units is less than the above sum, the standby operation unit number determination unit 26 does not input to the operation state determination unit 24.

Hereinafter, the number of fuel cells 10 required to output the predicted total power output is referred to as the "predicted required number". Furthermore, the sum of the number of normal mode fuel cells and the number of standby mode fuel cells at the current time (at the time when the predicted output command is input) is referred to as the "current operating number". Furthermore, the difference between the predicted required number and the current operating number is referred to as the "shortage operating number".

The operation state determination unit 24 receives the input of the insufficient number of operating units M from the standby operation unit number determination unit 26, and changes the stopped fuel cell 10 to the standby operation mode. In this case, the operation state determination unit 24 changes the fuel cell 10 with the least number of starts and stops among the stopped fuel cells 10 to the standby operation mode only for the insufficient number of operating units M calculated by the standby operation unit number determination unit 26. As a result, the fuel cell 10 is started only for the insufficient number of operating units M and operates in the standby operation mode. As a result, the fuel cell 10 that outputs a sufficient number of units for the predicted total power generation output operates in the normal operation mode or the standby operation mode.

Furthermore, when the operating state determination unit 24 receives the commanded normal mode number of units from the normal operation number determination unit 23, it calculates the difference between the commanded normal mode number of units and the number of normal mode fuel cells as the number of fuel cells operating in the normal operation mode that is insufficient for the output commanded total power generation output. This is also the number of fuel cells 10 that should be changed from the standby operation mode to the normal operation mode. Then, only the calculated number of standby mode fuel cells 10 is changed to the normal operation mode. Hereinafter, the number of fuel cells 10 that should be changed from the standby operation mode to the normal operation mode upon receiving the input of the commanded normal mode number of units is also referred to as "the number insufficient for the normal mode".

In this way, in the fuel cell system 1 of the second embodiment, the predicted output command is inputted periodically. Then, when the predicted required number of units is greater than the currently operating number of units, the stopped fuel cell is started up and operated in the standby operation mode. As a result, when the total power generation output is increased and the number of fuel cells 10 to be operated in the normal operation mode has increased, it is not necessary to change the standby mode fuel cell 10 to the normal operation mode, but also to start up the stopped fuel cell 10. As a result, the responsiveness of the power generation output of the fuel cell system 1 can be improved. Furthermore, when the stopped fuel cells 10 are switched to the standby operation mode, the fuel cell 10 with the least number of starts and stops among the stopped fuel cells 10 is started, thereby suppressing the bias in the number of starts and stops among the plurality of fuel cells 10. As a result, it is possible to suppress the situation where some of the plurality of fuel cells 10 deteriorate earlier than the other fuel cells 10.

Next, a control method of the fuel cell system 1 according to the second embodiment will be described with reference to Fig. 7 and Fig. 8. The process shown in Fig. 7 is performed regularly independently of the process shown in Fig. 8.

As shown in Fig. 7, the predicted output command is inputted periodically (e.g., at intervals of 20 minutes) from the operating device 30 to the predicted command acquisition unit 25 (step S21). The predicted output command indicates the predicted total power output that the fuel cell system 1 should generate in the future (e.g., between 20 minutes and 40 minutes later), as described above.

When the predicted output command is input to the predicted command acquisition unit 25, the standby operating unit number determination unit 26 calculates the number of fuel cells required to output the predicted total power generation output (predicted required number). Then, the calculated predicted required number is compared with the current number of operating units (step S22). In step S22, when the predicted required number is greater than the current number of operating units ("Yes" in step S22), the insufficient number of operating units M is calculated from the predicted required number of units and the current number of operating units. Then, the obtained insufficient number of operating units M is input to the operation state determination unit 24.

If the standby operating unit number determination unit 26 inputs that the number of operating units is less than the number M, the operating state determination unit 24 changes the fuel cell 10 that has been started and stopped the least times among the stopped fuel cells 10 to the standby operating mode only if the number of operating units is less than the number M (step S23). As a result, the fuel cell 10 is started and operated in the standby operating mode. In step S23, the operating state determination unit 24 transfers information on the operating state of each fuel cell 10 to the information acquisition unit 21.

Furthermore, in step S22, when the predicted required number of units is less than the current number of operating units ("No" in step S22), no input is made from the standby operating unit number determination unit 26 to the operating state determination unit 24. As a result, the activation of the stopped fuel cell 10 accompanying the input of the predicted output command is not performed.

After the processing shown in FIG. 7 , as shown in FIG. 8 , if the command acquisition unit 22 acquires the output command from the operating device 30 (step S11), the normal operation number determination unit 23 performs the judgment of step S12 in the same manner as in FIG. 4 . Then, if the answer of step S12 is “No”, the normal operation number determination unit 23 performs the judgment of step S13. If the answer of step S13 is “Yes”, the number of fuel cells in normal operation (the number of commanded normal mode units) required for the total power generation output of the output command is calculated.

Next, the normal operation unit number determination unit 23 calculates the number of fuel cells in normal operation that are short of the output command total power generation output (short for the number of normal mode units), and inputs the calculated value to the operation state determination unit 24. Next, in the operation state determination unit 24, the standby mode fuel cells 10 that are short of the number of normal mode units are changed to the normal operation mode (step S24). As a result, the fuel cells 10 that are short of the number of normal mode units are changed from the standby operation mode to the normal operation mode.

Furthermore, various changes can be made to the above-mentioned embodiment. For example, in the above-mentioned embodiment, the commanded total power output is any one of 0kW, 50kW, 100kW, 150kW, 200kW, 250kW and 300kW, but is not limited thereto. The commanded total power output can also be any value such as 42kW, 58kW, 142kW, etc. In this case, the normal mode fuel cell 10 can be operated at any power output if it is operated at 40% to 60% of its maximum power output. For example, when the maximum power output of each fuel cell 10 is 100kW and the commanded total power output is 42kW, a normal mode fuel cell 10 can also be operated at 42% of its maximum power output. Moreover, when the maximum power output of each fuel cell 10 is 100 kW and the commanded total power output is 142 kW, two normal mode fuel cells 10 can be operated at 50% of their maximum power output, and one normal mode fuel cell 10 can be operated at 42% of its maximum power output.

As described above, the fuel cell system 1 according to the first and second embodiments includes: a plurality of fuel cells 10, and a control device 20 for controlling the operating state of each fuel cell 10. Each fuel cell 10 can operate in a plurality of operating modes, and the plurality of operating modes include: a normal operating mode for operating with a power output having a power generation efficiency greater than a first power generation efficiency, and a standby operating mode for operating with a power output less than a second power generation efficiency lower than the first power generation efficiency. The control device 20 includes: a command acquisition unit 22, a normal operating number determination unit 23, and an operating state determination unit 24. The command acquisition unit 22 acquires an output command indicating the total power generation output that the fuel cell system 1 should generate. The normal operation number determination unit 23 determines the number of fuel cells 10 to be operated in the normal operation mode based on the total power output indicated by the output command. The operation state determination unit 24 determines the operation state of each fuel cell 10 based on the number determined by the normal operation number determination unit 23. When the total power output indicated by the output command is lower than the total power output generated by the fuel cell system 1, or when the number of fuel cells 10 determined by the normal operation number determination unit 23 is smaller than the number of fuel cells 10 operated in the normal operation mode, the operation state determination unit 24 changes the operation mode of at least one of the fuel cells 10 operated in the normal operation mode to the standby operation mode. Moreover, when the total power output indicated by the output instruction is higher than the total power output generated by the fuel cell system 1, or when the number of fuel cells 10 operated in the normal operation mode is greater than the number of fuel cells 10 operated in the normal operation mode, the operation state determination unit 24 changes the operation mode of at least one of the fuel cells 10 operated in the standby operation mode to the normal operation mode.

According to such a fuel cell system 1, the power generation efficiency of the fuel cell system 1 as a whole can be made to reach a predetermined power generation efficiency or higher. Furthermore, when the number of fuel cells 10 operating in the normal operation mode is greater than the number of fuel cells 10 required for the total power generation output indicated by the output command, the excess normal mode fuel cells 10 are not immediately changed to the operation stop state, but are changed to the standby operation mode. Alternatively, when the number of fuel cells 10 operating in the normal operation mode is less than the number of fuel cells 10 required for the total power generation output indicated by the output command, the fuel cells 10 operating in the standby operation mode are changed to the normal operation mode. By controlling the plurality of fuel cells 10 in this way, the chance of starting up the fuel cells 10 that are in a stopped state can be reduced while increasing the total power generation output of the fuel cell system 1. As a result, the responsiveness of the power generation output of the fuel cell system 1 can be improved.

In the fuel cell system 1 according to the first and second embodiments, the control device 20 further includes: an information acquisition unit 21 for acquiring the number of startups of each fuel cell 10. The operation state determination unit 24 changes the operation mode of the fuel cell 10 having the least number of startups acquired by the information acquisition unit 21 among the fuel cells 10 operating in the normal operation mode to the standby operation mode. The fuel cell 10 operating in the standby operation mode is highly likely to become an operation stop state later. Therefore, by changing the operation mode of the fuel cell 10 having the least number of startups to the standby operation mode, the occurrence of a bias in the number of startups among the plurality of fuel cells 10 can be suppressed. As a result, the occurrence of a part of the plurality of fuel cells 10 deteriorating earlier than the other fuel cells 10 can be suppressed.

In the fuel cell system 1 according to the first and second embodiments, the control device 20 further includes an information acquisition unit 21 that acquires the number of fuel cells 10 operating in the standby operation mode and the number of activations of each fuel cell 10. When the number of fuel cells 10 operating in the standby operation mode acquired by the information acquisition unit 21 is greater than a predetermined number N, the operation state determination unit 24 determines the fuel cell 10 operating in the standby operation mode, which has the smallest number of activations acquired by the information acquisition unit 21, as the fuel cell to be stopped. This can suppress the occurrence of bias in the number of activations among the plurality of fuel cells 10. As a result, it is possible to suppress the situation where some of the plurality of fuel cells 10 deteriorate earlier than the other fuel cells 10 .

In the fuel cell system 1 according to the first and second embodiments, the control device 20 further includes an information acquisition unit 21 that acquires the number of activations of each fuel cell 10. When the total power output indicated by the output command is higher than the total power output generated by the fuel cell system 1, or when the number of fuel cells 10 operated in the normal operation mode is greater than the number of fuel cells 10 operated in the normal operation mode, the operation state determination unit 24 determines the fuel cell 10 having the smallest number of activations acquired by the information acquisition unit 21 among the fuel cells 10 that have stopped operation as the fuel cell 10 operated in the normal operation mode. This can suppress the occurrence of bias in the number of activations among the plurality of fuel cells 10. As a result, it is possible to suppress the situation where some of the plurality of fuel cells 10 deteriorate earlier than the other fuel cells 10 .

In the fuel cell system 1 according to the second embodiment, the information acquisition unit 21 acquires the number of fuel cells 10 operating in the standby operation mode. When the number of fuel cells 10 acquired by the information acquisition unit 21 is less than the prescribed number (specifically, the difference between the estimated required number of fuel cells and the number of fuel cells in the normal mode at the time when the estimated output command is input), the operation state determination unit 24 determines the fuel cell 10 with the smallest number of activations acquired by the information acquisition unit 21 among the fuel cells 10 that have stopped operation as the fuel cell 10 that is operated in the standby operation mode. As a result, the chance of activating the fuel cell 10 that is in the stopped state while increasing the total power generation output of the fuel cell system 1 is more effectively reduced. As a result, the responsiveness of the power generation output of the fuel cell system 1 can be improved more effectively. Furthermore, the occurrence of a bias in the number of activations among the plurality of fuel cells 10 can be suppressed. As a result, the occurrence of a partial degradation of the plurality of fuel cells 10 earlier than the other fuel cells 10 can be suppressed.

In the fuel cell system 1 according to the first and second embodiments, when the fuel cell 10 is operated in the normal operation mode, it is operated at a power output of 40-60% of the maximum power output of the fuel cell 10. Thus, the power generation efficiency of the entire fuel cell system 1 can be effectively improved.

In the fuel cell system 1 according to the first and second embodiments, when the fuel cell 10 is operated in the normal operation mode, the fuel cell 10 is operated with the power generation efficiency of the fuel cell 10 as the maximum power generation output. Thus, the power generation efficiency of the entire fuel cell system 1 can be more effectively improved.

In the fuel cell system 1 according to the first and second embodiments, when the fuel cell 10 is operated in the standby operation mode, it is operated at a power generation output of 5 to 15% of the maximum power generation output of the fuel cell 10 .

The control method resulting from the first and second embodiments is a control method for a fuel cell system 1, the fuel cell system comprising a plurality of fuel cells 10, each of the plurality of fuel cells being operable in a plurality of operation modes, the plurality of operation modes comprising: a normal operation mode in which the system operates at a high-efficiency power output having a power generation efficiency greater than or equal to a first power generation efficiency, and a standby operation mode in which the system operates at a low-efficiency power generation output less than or equal to a second power generation efficiency lower than the first power generation efficiency. The control method comprises: an output instruction acquisition process, a normal operation number determination process, and an operation state determination process. In the output instruction acquisition process, an output instruction representing the total power generation output to be generated by the fuel cell system 1 is acquired. In the normal operation number determination process, the number of fuel cells 10 to be operated in the normal operation mode is determined based on the total power generation output represented by the output instruction. In the operation state determination step, the operation state of each fuel cell 10 is determined based on the number of units determined in the normal operation number determination step. Specifically, in the operation state determination step, when the total power output indicated by the output command is lower than the total power output generated by the fuel cell system 1, or when the number of fuel cells 10 determined in the normal operation number determination step is less than the number of fuel cells 10 operating in the normal operation mode, the operation mode of at least one of the fuel cells 10 operating in the normal operation mode is changed to the standby operation mode. Moreover, in the operation state determination process, when the total power output indicated by the output instruction is higher than the total power output generated by the fuel cell system 1, or when the number of fuel cells 10 determined in the normal operation number determination process is greater than the number of fuel cells 10 operating in the normal operation mode, the operation mode of at least one of the fuel cells 10 operating in the standby operation mode is changed to the normal operation mode.

According to such a control method of the fuel cell system 1, the power generation efficiency of the entire fuel cell system 1 can be made to reach or exceed the prescribed power generation efficiency. Furthermore, when the number of fuel cells 10 operating in the normal operation mode is greater than the number of fuel cells 10 required for the output total power generation output indicated by the output command, the operation of the excess normal mode fuel cells 10 is not immediately stopped, but the system is changed to the standby operation mode. Alternatively, when the number of fuel cells 10 operating in the normal operation mode is less than the number of fuel cells 10 required for the output total power generation output indicated by the output command, the fuel cells 10 operating in the standby operation mode are changed to the normal operation mode. By controlling the plurality of fuel cells 10 in this way, the chance of starting up the fuel cells 10 that are in a stopped state can be reduced while increasing the total power generation output of the fuel cell system 1. As a result, the responsiveness of the power generation output of the fuel cell system 1 can be improved.

Several embodiments and variations of the present invention are described, but these embodiments and variations are provided as examples only and are not intended to limit the scope of the invention. These novel embodiments and variations can be implemented in various other forms, and can be omitted, replaced, and changed in various ways without departing from the gist of the invention. These embodiments or variations thereof are included in the scope or gist of the invention, and are also included in the invention described in the patent application and its equivalent. Moreover, it is natural that some of these embodiments and variations can be appropriately combined within the scope of the gist of the present invention.

1: Fuel cell system 10: Fuel cell 11: Fuel cell stack 12: Anode 13: Cathode 20: Control device 21: Information acquisition unit 2: Command acquisition unit 23: Normal operation number determination unit 24: Operation status determination unit 30: Operation device

[ Fig. 1] Fig. 1 is a block diagram showing the structure of a fuel cell system according to a first embodiment of the present invention.

[Fig. 2] Fig. 2 is a diagram showing the configuration of a fuel cell included in the fuel cell system shown in Fig. 1.

[Fig. 3] Fig. 3 is a diagram showing the configuration of a control device for the fuel cell system shown in Fig. 1.

[Fig. 4] Fig. 4 is a flow chart showing a control method of the fuel cell system according to the first embodiment.

[Fig. 5] Fig. 5 is a flow chart showing a method for controlling a fuel cell system according to the first embodiment.

[Fig. 6] Fig. 6 is a diagram showing the structure of a control device for a fuel cell system according to a second embodiment.

[Fig. 7] Fig. 7 is a flow chart showing a method for controlling a fuel cell system according to the second embodiment.

[Fig. 8] Fig. 8 is a flow chart showing a method for controlling a fuel cell system according to the second embodiment.

1: Fuel cell system

10: Fuel cell

20: Control device

30: Operating device

Claims (9)

A fuel cell system comprises: a plurality of fuel cells; and a control device for controlling the operation state of each fuel cell using a control system configured in series; wherein: each fuel cell can be operated in a plurality of operation modes, and the plurality of operation modes include: a normal operation mode in which the power generation efficiency is operated at a power output of a first power generation efficiency or higher, and a power generation efficiency is operated at a second power generation efficiency or lower than the first power generation efficiency. The control device comprises: an instruction acquisition unit, which acquires an output instruction indicating a total power output to be generated by the fuel cell system; a normal operation number determination unit, which determines the number of fuel cells to be operated in the normal operation mode according to the total power output indicated by the output instruction; and an operation state determination unit, which determines the number of each fuel cell according to the number determined by the normal operation number determination unit. the operating state of the fuel cell; when the total power output indicated by the output instruction is lower than the total power output generated by the fuel cell system, or when the number of fuel cells operated in the normal operation mode is less than the number of fuel cells determined by the normal operation number determination unit, the operating state determination unit changes the operating mode of at least one of the fuel cells operated in the normal operation mode to the standby operation mode. When the total power output indicated by the output command is higher than the total power output generated by the fuel cell system, or when the number of fuel cells determined by the normal operation number determination unit is greater than the number of fuel cells operating in the normal operation mode, the operation state determination unit changes the operation mode of at least one of the fuel cells operating in the standby operation mode to the normal operation mode. The fuel cell system of claim 1, wherein the control device further comprises: an information acquisition unit for acquiring the number of activations of each fuel cell; and the operation state determination unit changes the operation mode of the fuel cell operating in the normal operation mode and having the least number of activations acquired by the information acquisition unit to the standby operation mode. The fuel cell system of claim 2, wherein the control device further comprises: an information acquisition unit for acquiring the number of fuel cells operating in the standby operation mode and the number of activations of each fuel cell; when the number of fuel cells operating in the standby operation mode acquired by the information acquisition unit is greater than the prescribed number, the operation state determination unit determines the fuel cell operating in the standby operation mode with the least number of activations acquired by the information acquisition unit as the fuel cell to be stopped. The fuel cell system of claim 3, wherein the control device further comprises: an information acquisition unit for acquiring the number of activations of each fuel cell; When the total power output indicated by the output command is higher than the total power output generated by the fuel cell system, or when the number of fuel cells operated in the normal operation mode is greater than the number of fuel cells operated in the normal operation mode, the operation state determination unit determines the fuel cell with the least number of activations acquired by the information acquisition unit among the fuel cells that have stopped operation as the fuel cell operated in the normal operation mode. A fuel cell system as claimed in claim 4, wherein the information acquisition unit acquires the number of fuel cells operating in the standby operation mode; when the number of fuel cells acquired by the information acquisition unit is less than the specified number of fuel cells, the operation state determination unit determines the fuel cell with the least number of startups acquired by the information acquisition unit among the fuel cells that have stopped operation as the fuel cell operating in the standby operation mode. A fuel cell system as claimed in any one of claims 1 to 5, wherein the fuel cell operates at a power output of 40 to 60% of the maximum power output of the fuel cell when operating in a normal operation mode. A fuel cell system as claimed in any one of claims 1 to 5, wherein when the fuel cell is operated in a normal operation mode, the fuel cell is operated at a power output with a maximum power generation efficiency. A fuel cell system as claimed in any one of claims 1 to 5, wherein, when the fuel cell is operated in a standby operation mode, it operates at a power output of 5 to 15% of the maximum power output of the fuel cell. A control method for a fuel cell system is to use a control system configured in series to control the fuel cell system, wherein the fuel cell system includes a plurality of fuel cells, each of the plurality of fuel cells can be operated in a plurality of operation modes, the plurality of operation modes including: a normal operation mode in which a high-efficiency power generation output is operated with a power generation efficiency higher than a first power generation efficiency, and a second power generation efficiency lower than the first power generation efficiency. The control method comprises: an output instruction acquisition step, which is to acquire an output instruction indicating the total power output to be generated by the fuel cell system; a normal operation number determination step, which is to determine the number of fuel cells to be operated in the normal operation mode according to the total power output indicated by the output instruction; and an operation state determination step, which is to determine the number of fuel cells to be operated in the normal operation mode according to the total power output indicated by the output instruction; In the operation state determination step, when the total power output indicated by the output command is lower than the total power output generated by the fuel cell system, or when the number of fuel cells operated in the normal operation mode is less than the number of fuel cells operated in the normal operation mode, at least one of the fuel cells operated in the normal operation mode is switched off. The operation mode is changed to the standby operation mode; When the total power output indicated by the output instruction is higher than the total power output generated by the fuel cell system, or when the number of fuel cells operated in the normal operation mode is greater than the number of fuel cells determined in the normal operation number determination step, the operation mode of at least one of the fuel cells operated in the standby operation mode is changed to the normal operation mode.

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